AD — A two-knob envelope: attack, decay. Snappy plucks, percussive shapes…

Modulators

A two-knob envelope: attack, decay. Snappy plucks, percussive shapes, the simplest way to make a note rise and fall.

What is a AD?

AD is the simplest envelope: two stages, two knobs, three jacks. A trigger on the GATE input fires the envelope - it rises during Attack, then falls during Decay back to silence. There is no sustain stage. This is the canonical "shape over time" reduction: the foundation behind plucks, drum hits, and any sound that decays naturally. The first module in the Basic series, designed to teach envelope shaping with as little surface area as possible. When you outgrow it, ADSR adds sustain, release, CV inputs, and an inverted output.

In a patch

Patch a clock, sequencer gate, or Euclidean trigger into GATE. Send ENV out to a VCA CV input to shape volume - your saw or square wave becomes a pluck. Default values (Attack 1ms, Decay 200ms) give a snappy pluck right out of the box. Crank Decay up for longer-tailed notes; turn Attack up for swells. Patch ENV into a filter cutoff CV for "wow" / talkbox-style sweeps that follow each note. EOC fires a 1ms pulse when Decay completes - chain it into another AD's GATE for two-stage envelopes, or into a sample-and-hold trigger for stepped modulation. Need an inverted envelope? Run ENV through an Attenuverter set to -1.

Inputs

Gate (gate) — Trigger input. Every rising edge (signal crosses 2.5V going up) fires the envelope: ATTACK starts, then DECAY runs to 0. Eurorack-standard 0-10V gate threshold. Trigger-style retrigger: a new rising edge mid-envelope restarts ATTACK from the envelope's current level (no clicks, no zero-snap). Holding GATE high after the first trigger does NOT retrigger - you must release and re-fire to start a new cycle. Works cleanly from clocks, SEQ8 gate outputs, Euclidean rhythm generators, and any 0-10V gate stream.

Outputs

ENV (cv) — Main envelope output, unipolar 0-10V. 0V at idle, rises to 10V during ATTACK, falls back to 0V during DECAY. Patch into a VCA CV input for volume shaping (the canonical use), or into a filter cutoff CV to create "wow" sweeps that track each note. Also useful for pitch sweeps (into a VCO FM input) and for triggering visual modulation on a Scope.
EOC (gate) — End-of-cycle trigger. Fires a 1ms 10V pulse the moment DECAY completes (envelope returns to idle). Useful for chaining: feed EOC into another AD's GATE to build a two-stage A1-D1-A2-D2 shape, or into a sample-and-hold trigger to step a modulation source. Holds at 0V outside of that 1ms pulse.

Controls

A — Attack time. Range 1ms-8s, exponential scale. How quickly the envelope rises from current level toward 10V after a trigger. 1ms is instantaneous (snappy plucks, drum hits); 5-50ms gives a soft "huff" attack on bass; 100ms-1s creates audible swells; 1-8s for slow pad-like fades. The exponential curve means most of the rise happens early, then asymptotes - good for natural-sounding attacks.
D — Decay time. Range 1ms-8s, exponential scale. How long the envelope tail lasts after reaching peak. 1-50ms for percussive ticks and snare clicks; 100-300ms for plucks and short notes; 500ms-2s for longer-tailed notes and bass drops; 2-8s for ambient washes. Same exponential curve as Attack - the envelope reaches near-zero in roughly 9 time-constants, so a 200ms Decay takes ~1.8s to fully complete.

Inspired by

Two-stage trigger-style envelope. Rising edge starts attack, decays to rest, EOC pulse on completion. Foundational to percussion, plucks, and the "shape over time" lesson - the simplest reduction of an envelope generator.

Make Noise Function
Mutable Instruments Stages (AD mode)

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